Analysis of the dry dipterocarp forest vegetation in Thailand
1982
Somsak Sukwong (Kasetsart Univ., Bangkok (Thailand). Faculty of Forestry)
Overstory and physical environmental factor data were collected from 52 stands in the undisturbed Dry Dipterocarp forests in the north, north-east and south-west of Thailand. The stand basal areas ranged from 7.5 to 39.8 m to the second power per hectare depending on the leading dominant species. Results revealed that the basal area for Shorea-Pentacme forest averaging 12.0 for a xeric form and 22.5 m to the second power per hectare for a mesic form, the Dipterocarpus obtusifolius-tuberculatus 22.9 m to the second power per hectare, the mixed Dry Dipterocarp forest 26.7 m to the second power per hectare, the Pine-Dipterocarp forests averaging 20.2 and 27.0 m to the second power per hectare for a xeric and mesic form respectively. The average total number of trees greater than 10 cm dbh ranged from 425 to 520 per hectare for these four associations. The xeric forms of Dry Dipterocarp forests were richer in small trees (10-20 cm dbh) which accounted for more than a half out of total number. Stand basal area data showed sufficiently significant correlation with average stand height. Topographic and soil parameters were used to develop predictive equations for the basal area per hectare. Regression analysis revealed that there appeared the positive relationship between basal area per hectare with the soil pH, organic matter, depth of root penetration and elevation. On the other hand, magnesium, sodium and slope produced the negative relationships with stand basal area.
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